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. Author manuscript; available in PMC: 2015 Sep 1.
Published in final edited form as: Nat Rev Drug Discov. 2014 Aug 8;13(9):655–672. doi: 10.1038/nrd4363

Figure 4. FcRn recycling mechanism.

Figure 4

Neonatal Fc receptor (FcRn) recycling has a crucial role in the biological activity of Fc- and albumin-fusion proteins. Fc-fusion protein drugs or albumin-fusion protein drugs bind to FcRn on the endothelium. Receptor-bound proteins are internalized into endocytic vesicles. End osomes are acidified and undergo sorting of FcRn. Non-receptor-bound proteins are degraded in the lysosomal compartment and receptor-bound proteins are recycled back to the cell membrane. The protein therapeutic is subsequently released back into the blood. FcRn-mediated recycling leads to prolonged circulation of Fc-fusion and albumin-fusion protein therapeutics. IgG, immunoglobulin G.